Study Reveals Variation in Accuracy of Laboratory Blood Testing Results

More than half of the blood tests analyzed from LabCorp, Quest Diagnostics, and Theranos showed significant differences.

Researchers from Mount Sinai Hospital compared basic blood tests run by commercial laboratories and found that testing time and service significantly influenced the results of the test.

In their study, the researchers analyzed results from comparable blood tests from 60 healthy adults conducted at LabCorp, Quest Diagnostics, and Theranos. They collected multiple samples from the same individuals at an ambulatory clinic and at retail outlets with point-of-care services in Phoenix, Arizona. The analysis was controlled for age, sex, and time of blood collection.

“While most of the variability we found was within clinically accepted ranges, there were several cases where inaccurate results would have led to incorrect medical decisions,” senior author Joel Dudley, director of Biomedical Informatics at the Icahn School of Medicine at Mount Sinai noted in a prepared statement about the study.

“We hope this study will inspire the biomedical community to take a critical look at all testing variables to ensure that lab results are as robust and reproducible as possible.”

Of the 22 lab measurements that were evaluated for uncertainty and accuracy, 15 (68%) showed significant interservice variability (P<.002). Theranos flagged blood test results outside of their normal range 1.6 times more often than the results from LabCorp or Quest Diagnostics.

The researchers noted that triglyceride levels and red blood cell count were the most consistent test results, and white blood cell count and total cholesterol levels showed the most variation. They also noted that blood samples obtained earlier in the day showed significant differences compared with samples obtained later in the day from the same individuals.

The study used common blood tests, which return a single or a couple of data points. However, the study collected 14 samples from 60 participants to generate 22 lab measurements for each individual, which resulted in 18 480 potential measurements.

Lab tests are used to determine disease diagnoses and medication treatments, meaning that even a small amount of inaccurate data in blood tests could lead to additional errors in scientific and clinical studies.

“These testing disparities occurred despite rigorous laboratory certification and proficiency standards designed to ensure consistency,” co-senior author Eric Schadt, PhD, the Jean C. and James W. Crystal Professor of Genomics at the Icahn School of Medicine and founding director of the Icahn Institute for Genomics and Multiscale Biology, said in the statement.

“Our results suggest the need for greater transparency in lab technologies and procedures, as well as a much more thorough investigation of biological mechanisms that may contribute to more dynamic levels than we currently understand.”


  1. Kidd BA, Hoffman G, Zimmerman N, et al. Evaluation of direct-to-consumer low-volume lab tests in healthy adults. J Clin Invest. 2016. doi: 10.1172/JCI86318.